the only thing I have read is just use skim milk, if you use any other kind, all the fat can slow absorbtion rate of the protein and you body may miss the protein assimilation in its "anabolic window".

not really, small amounts of fat in liquid form have a minimal effect on protein absorption.

here's some info on this

The majority of delay when it comes to fats is either

a) When they are in a solid state and it delays the breakdown of bolus (solid like state) into chyme (semi-liquid) state. With a shake, this process is already complete so that delay is almost nonexistant....Think of red meat and the difference in fats vs. oils.

b) The emulsification of saturated or transfatty acids within the small intestine. At this point the absortion of amino's is already taking place.

So in general when your fat amount is about 1-2tblsp within a liquid state already (thanks to your blender) the delay in amino absortion is almost non-existant.

Whole foods are where fats delay digestion the most. Even then the actual absortion of nutrients (amino's specifically) isn't altered that much. The process of breaking down whole foods and trasnfering them to the lower part of the stomach and into the small intestine is just a much slower process because of its makeup.

As long as you get something to eat 1-2h after your workout and that it has protein it's fine. Milk is also good because it elicits a much bigger insulin response than it should considering its carb content so it favors an anabolic environment.